Rotary pump



Nov. 3, 1953 c. L. ENGLISH ROTARY PUMP 3 Sheets-Sheet l Filed April 12, 1948 C. L. ENGLISH ROTARY PUMP Nov. 3, 1953 3 Sheets-Sheet 2 Filed April l2, 1948 \f\ lll.,

INVENToR. War/e5 L /rg///v AHORA/fx y C. L. ENGLISH Nov. 3, 1953 ROTARY PUMP 5 Sheets-Sheet 5 Filed April l2, 1948 INI/ENTOR. Char/e5 L f/gy//s/f n? ,4 70m/EK Patented Nov. 3, 1953 atmet RQTARY BUMP Tulsa! 919e-, assigner, by mi;` "Las Anklets `.aitor'rfi'iiiil Deaver? Application April l2, 1948, -Swerialllgs v@(54997 ricains.. (C1-19.37.1.24)

yBroadly speaking, it is :the abject `Qf in? Ili vention to provide .a new type of .rotar-yp mp whichis-simple .yetrugged in construiipn, ich can be manufactured economically, and eiilcientl and trouble-free in .operaiqne Another Objectis `tc .proyide a rotary .pump mechanism having 7very vlittle friction .whereby it will give long .service with a Lminimum of picar. A further-Objectis to provide a mechanism ythat automatically compensates for suchwg a5' .(19.65 `taire place and consequently maint ns its lepfeiency in use. '.Stillanothernbject .i toprgyide a pump Vadapted .to operate witha minimum of Villera-tion` A further object is .to proyidea plimp'hlllg all the advantages of conventional ring .gearand-pinion .rotary pumps, :but `having less ,friction and greater efficiency, lessfwear .andlonger life, and no inherent limitationrnponcapacity.

`In -general,-my .pump is of. .the .type -hailing an annular, .ported rotor .encircling aeCOILd lQr eccentric .relation .'thereto. An Iimp@:Giant y'-feature of the invention resides'in the .provisioazbr tween the two rotors, of aseriesrof independently movable members which serve `'to .transmit the rotation of one rotor .'-to .the other, .and which also serve as vanes or partitions subdividing the space 'between vthe rotorsinto ,a series ofcham- VVbers each adaptedV to .alternately increase and decrease in volume; according to .the ,invention thesemembers are cylindershaving a rolling eny .gagemen-t .with the-.respective rotors, whereby the --friction between the rparts is negligible.

A nother feature :lies in the structureand relationshipof parts whereby the rollers Aor .vanes are self-adjustingin position, and automatically other.

Other objects .ofthe invention, together with furtherffeatures .of novelty, .will appear .in the company-ing drawingsV which forma part ,of vthe specification and are '.vto be read conjunction therewith, and in which like reference numerals kare employed to indicatefl'ike parts ,cf the-various views: .'Fig. .1 is .an axialcross sectign. Qf @ne f Qlmpf -seat themselves inthe Vfashion .best adapted to 450 Vseal adjacent ones lof saidchambers from each course of the Afollowing description. In the -ac- '$5 the .minacce et ro' enticing soja, to

Eig. 8 is an.

Referring generally .to the Lpumps shown in the dra-wires., the .essential .operating mmenim 'in ll casA c prises a pairofcocperatingfcomf t rQt ,but m .so Pilat me ivo m. relationship. n 4. u [l v Equally spaceifarundthe periphery 9i the inner rotor Aare :a .s ries of *arialv vgrooves I4 oc- ,cu dby cylinlrcal.,rollervarieslli.- The 'inner ry .or ,here lof rotor 12 ris provided with ondingaxxialfgrooves EI 8, and in theh'regi'n closest to lone another .with the gl'QOves 'inboth members, 'irisvr'e that the two `members move together. Either ther` inner .or the @aber ,feier may be .ihedrliifef s" Will'be madeclear ,pr ently, the rollers in'either fca's'e se, ine .i9 transmit the Vr.f. iitif r1 .of ihdiir iofirieiller--membsr- It will be observed that the total number of ,f .reliefs .L .by-Dee- ,Ailsach riceve I8 e or port 2p extending l y A communicate `with'the r1 @hanter 2.2 an@ .the sure chamber Hamper gressively increase in volume on the side adjacent suction chamber 22 and accordingly the fluid is drawn from the latter chamber through ports 20 into the space between the rotors. On the opposite side of the pump, the compartments between the rollers decrease progressively in volume, forcing the fluid back through the same ports 20 into the pressure chamber, as will be described more in detail hereinafter. The uid being pumped enters the suction chamber or manifold through the pump inlet 26 and leaves the pressure chamber or manifold through the pump outlet 28.

Turning to Figs. l to 4, the ,structural details of the pump there illustrated now will be considered more in detail. Its housing is made up of a. central block 30 and a pair of flanged, shaftsupporting hubs 32 and 34; the annular flanges 36 on the latter members are seated in shallow circular recesses in opposite faces of the block and are secured in place by a series of bolts 31 extending through each flange into the body of the block.

In the hubs 32 and 34 are sleeve bearings 38, each having an external annular flange recessed into the end of the hub so that the flanged end of the bearing is flush with the inner face of the hub. These bearings support the shaft 40 which has rotor I keyed thereto.

Between the adjacent inner faces of the respective hub members, block 3l) has a circular bore adapted to receive the outer rotor or ring I2. The axis of this bore (hence the axis of the ring) is spaced below the axis of shaft 4E), whereby the two rotating members are in eccentric relationship as hereinbefore mentioned. The suction and pressure manifolds of the pump are formed by circumferential channels 22 and 24 in the bore of block 3B, these channels registering with apertures 2B in the ring. The respective ones of the channels communicate with inlet and outlet ducts 26 and 28, as shown.

To prevent leakage of fluid from the pressure manifold to the suction manifold through the clearance around ring I2, a pair of self-adjusting sealing members 42 are provided. Disposed in semi-cylindrical grooves running parallel to the axis of the bore, these are free to swivel slightly and have concave faces adapted to seat against the periphery of the ring.

The ends of the pump housing may be closed in any suitable fashion, for example by end caps 44 and 46 as shown the former cap, apertured to receive the shaft, has internal threads 'by means of which it is screwed in place while the latter is bolted to the housing. A weal` plate 48 is clamped between cap 46 and an annular offset in the bore of the hub. A thrust ring 50 is pinned to the shaft to oppose the thrust of the discharge pressure reacting against the cross sectional area of the shaft diameter passing between the packing 52. At the other end of the housing there is a packing gland or rotary seal 52 of conventional form.

The direction of the pumps rotation and the direction of the fluid flow are indicated by arrows in Fig. 2. In this model of pump, the power is applied directly to the rotor ID by means of a motor or prime mover (not shown) connected to shaft 40, and, as previously explained, the rotor in turn drives ring I2 due to the meshing of rollers I6 with grooves I4 `and I8 in the respective members in the region where the ring and inner rotor are closest to one another.

Because of their intermeshed condition in this region it will immediately be apparent that the linear or circumferential speed of the inner and outer members is the same; however, having a somewhat smaller circumference than the bore of the ring I2, the rotor turns at a slightly higher angular velocity than the ring in maintaining an equal circumferential speed. Centrifugal force urges rollers I6 outwardly against the interior of the ring, and they therefore roll along the interior of the ring, advancing progressively relative to the grooves I8 due to the difference in angular velocity of rotor I0 and ring I2. This difference is such that any roller I6 will advance from one groove I8 to the next groove in the course of each complete revolution of rotor I0.

The orbit of the rollers I6 is very nearly circular, but inasmuch as each roller moves gradually away from the axis of rotor Ill during one half revolution of the rotor and then moves gradually back toward the axis during the ensuing half revolution, their orbit obviously is eccentric to the rotor. It will be evident that this nearcircular orbit has its center intermediate the axes of the inner and outer rotors.

The maximum radial travel of the rollers in their individual grooves I4 is determined by the relative dimensions of the cooperating parts, and can be changed by modifications in design, as will be explained more in detail presently. However, it should be noted that the radial travel of the rollers always is somewhat less than the maximum gap between the inner and outer rotors. Considering the rollers as vanes serving to dam off the gap between the inner and outer rotors, the fact that this result can be obtained with comparatively little radial movement of the rollers I6 is important for the reason that it minimizes the vibration which otherwise might take place due to the eccentricity of the rollers orbit relative the axis of shaft 4|).

If desired, the rollers can be made of plastic or other light material rather than metal, in order to further enhance the smoothness of operation; the use of these lighter and cheaper materials also has certain commercial advantages, and inasmuch as there is little friction or abrasive action on the rollers, such alternative materials serve very satisfactorily.

The operation of the pump should be comparatively plain from the foregoing description. Referring to Fig. 2, it will be seen that the fluid entering the suction manifold 22 through inlet 26 passes through apertures 20 into the space between the inner and outer rotors as already described. As each aperture 20 in turn passes over the lowermost seal 42, the rollers I6 on either side of that aperture, together with the inner and outer rotor, form a small, completely closed cavity 54 transporting the fluid contained therein to the pressure side of the pump, the fluid then being forced out through the aperture into the manifold 24 when said aperture clears the seal and comes into register with the manifold.

Attention is directed to the fact that the roller indicated at Ita, (Fig. 2) serves as a dam between the high pressure fluid in chamber 24 and the low pressure fluid in cavity 54. To insure that it forms a tight seal between the differing pressure zones, a pair of grooves 56 are provided in the leading wall of the roller retaining socket I4; these admit the high pressure fluid from chamber 24 to the region behind the roller, forcing it outwardly and rearwardly so that it seats firmly on the inner wall of ring I2 and the trailing edge of its retaining socket. Each roller in passing ansiosa through the critical region vin which roller I6a. is shown has the sameimportant sealing function to perform, and all of them are automatically urged into the best sealing relation with the two rotors in similar fashion by pressure of the fluid behind the rollers, it being understood that this supplements the centrifugal force always acting upon the rollers.

Turning now to Figs. 5 to '7, the pump there shown embodies the basic principles explained above and the essential construction of the rotors and roller vanes is similar to that in the pump kalready described. Here, however, the rotary ring l2 is provided with annular end plates 58 which are bolted to the ring and form therewith a cage lenclosing the inner rotor I8 and rollers I6. Integral with these plates are outwardly extending vhollow trunnions-BD jour-nalled in external sleeve bearings 62; the latter bearings are recessed in the pump housing members 64 which in turn are bolted to the central housing part 66. Thus it will be seen that instead of floating freely in the bore of the central housing part as ring I2 does in the construction illustrated in Figs. 1 and 4, the outer rotor cage in Figs. 5 to '7 is positively `supported on external bearings which maintain the -cage very accurately positioned relative the associated mechanism.

The shaft `lli) of the inner rotor I-0 is supported on flanged sleeve bearing-s 68, the flange on these bearings being clamped between housing parts 64 and '10. Thelast-mentioned parts also sup- -port packing glands lor seals 1.2 for the rotating shaft and have annular end caps 14 bolted thereto to maintain the seals in place.

Power applied to either end of shaft 40 turns rotor I0 clock-wise (Figs. -6 Vand 7) and the rotor, through the medium of Y'rollers .I6 meshing with grooves I8 in Iring |12, serves to drive the cage. The manner in which these cooperating rotors "and roller vanes draw fluid into the suction cavity 22 lthrough inlet 21B and expelit from pressure chamber 24 through outlet 28 will be understood ,from the explanation that'has gone before.

Figs. r8 and 9 show a modified form of pump wherein the external prime mover is connected directly to the outer rotor and this in turn drives the inner rotor. The outer rotor lf2 -is a cylindrical cup integral with the drive shaft 40', the shaft being supported by two spacedsets of tapered roller bearings I6 disposed in housing member 18. vThe inner rotorl I 0 is `integral with a stub shaft -80 supported in housing member 82 by spaced `sets of roller bearings 84. Housing members 'I8 and `82 .are bolted ytoV opposite sides of the rcentral housing section 85, as shown.

Encircli-ng stub shaft 80 are a pair of collars -86 vand '88 secured to the inner rotor by bolts 90; these extendradially outward beyond the Amargin of rotor y|tl so .that they are adjacent the edge of outer rotor I2, and -they contain offsets between which are clamped `sealing rings 92. The latter rings cooperate with a fixed annular Iseat v94 in housing 82 inforder to prevent leakage into the bearing cavityof the fluid being pumped. It will be observed that the outer races of the bearings 84 are clamped between end cap 96 and an inwardly extending radial flange on seat 94, `the sleeve 9B serving to maintain them properly spaced. An integral axial flange on collar 88 forms an abutment shoulder for holding one of the inner races in place, lthe other inner race being secured `by .a disk '|00 boltedto the end of .thestub shaft.

, 6 lar sealing rings |02, cooperating with an annular seat |04. The outer races of 'bearings '16, spaced apart by sleeve |06, are clamped between the seat and a shoulder on end piece |08. A split ring I I0 occupying a groove I I2 in the shaft and an internally threaded nut ||4 `maintain one of the inner races in position, while the sealretaining member IIB holds the other. Numeral II8 identifies a packing gland around shaft 40' for further insuring against leakage.

In operation, pOWer is applied to shaft 40" to turn the outer rotor l2 clock-wise (Fig. 9) and this, due to the meshing of rollers I6 with grooves Ill and I8 drives the inner rotor I0. The fluid is drawn into the pump through inlet 26 anddischarged through outlet 28 all as described hereinbefore.

It will be observed that the'purnp of Figs. 8 and 9 employs six roller vanes, while the pump of Figs. 1 to 4 employs seven and the pump of Figs. 5 to '7 employs eight. In every case the total number of grooves I8 in the outer rotor vor ring is one greater than the total number of rollers employed, so the angular velocities of the inner and outer rotors are in the ratio of 6:"7 in the structure of Figs. 8 and '9; in the ratio of 7:8 in Figs. 1 to 4; and 'in the ratio of 8:9 in Figs. 5 to 7. rThis is intended merely to be illustrative of the variation vin ratio that may be embodied in the pump mechanism, other ratios obviously being obtainabl'eby using a 'larger or smaller number of rollers.

Referring to Fig. .6, it will be observed'tha't the relative depth of groovesof I4 and` I8 is such that rollers I6 at the top ofltheir orbit are largely within the peripheral outline of 'the inner rotor. The total depth of fthe'two 'registering `grooves must, of course, be .substantially equal to the diameter of the roller; however this 'total depth may be divided between the inner and outer grooves in other proportions than illustrated. which is to say the outer groove maybe made deeper and theA inner groove shallower, or vice versa. In general, the more nearly the inner and outer grooves approach being equal in depth (see for instance, Fig. 2) the less will 'be the radial travel of the rollers l5 relative the axis of rotor It in the course of the revolution ofthe latter.

Other possible modifications in structural details of the pump will be evident to those versed in the art; for example, either the intake vmanifold 22 or the discharge manifold 24 can'be varied in size so as to register with va larger or smaller fraction of the outer rotors circumference. ln working with compressible fluids it ordinarily is desirable to make the discharge manifold of suoli size that the individual ports 28 register with it only through approximately V30 degrees of each revolution.

Pumps embodying the features set forth above can be made in an exceedingly wide range Vof sizes, inasmuch as the roller vane construction embodies no inherent limitation upon size. By actual test the pumps havebeen found to operate with a minimum of vibration.

As pointed out hereinbefore, it is practical to make the rollers I6 of metal or, alternately, of molded plastic, hard rubber or the like, the latter materials having the advantage of lightness and economy. VWhatever substance is used, 'the rollers have an important advantage over conventional vanes in that their ,rolling contact with the two pump rotors veri/.materially reduces friction and wear.

Around shaft 40 adjacent to rotor l2 are simi-'515' 'Some wearing of the rollers over a period of time is, of course, inevitable, but even this does not impair the pumps operation for the reason that due to centrifugal force and the pressure of fluid admitted behind the rollers they automatically adjust themselves to their best seating position. Thus the pumps will maintain their eniciency and give satisfactory service over long periods of time without maintenance. The selfseating characteristic of the roller vanes also obviates maintaining close tolerances in the manufacture of the pump mechanism, a factor which is very important in reducing manufacturing costs.

From the foregoing it will be seen that this invention is one well adapted to attain all the ends and objects hereinbefore set forth, together with other advantages which are obvious and which are inherent to the apparatus.

It will be understood that certain features and subcom'binations are of utility and may be employed without reference to other features and subcombinations- This is contemplated by and is within the scope of the claims.

Inasmuch as many possible embodiments of the invention may be made without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

Having thus described the invention, I claim:

1. In a rotary pump, a pair of rotors interconnected for rotation in predetermined angular relationship, one of said rotors comprising a perforate annulus encircling the other, said rotors supported in eccentric relation whereby there is a crescent-shaped gap between them, an intake manifold and an exhaust manifold adjacent the exterior of the annulus and communicating with the perforations therein, the inner rotor having around its periphery a series of circumferentially spaced pockets, and a free-floating roller in each pocket urged outwardly by centrifugal force as the inner rotor turns whereby said rollers always ride against the interior of said annulus and subdivide said crescent-shaped gap into a plurality of separate compartments.

2. A pump as in claim 1 wherein the bore of said annulus is provided with circumferentiallyspaced pockets for receiving said rollers, the depth of the latter pockets being less than the radius of the individual rollers whereby rollers seated partly in pockets in the annulus and partly in pockets in the inner rotor maintain the two rotors in predetermined angular relationship.

3. A pump as in claim 1 wherein a power driven shaft is connected directly to the inner one of said rotors, having mechanism including said rollers for transmitting the rotation of said inner rotor to said annulus.

4. A pump as in claim 1 wherein a power driven shaft is directly connected to the outer one of said rotors, having mechanism including said rollers for transmitting the rotation of said outer rotor to said inner rotor.

5. In a rotary pump, a housing having a circular bore, a rotating perforate annulus in said bore, the bore of said housing having a pair of spaced, circumferential channels registering with the perforations in the annulus, an eccentric rotor in said annulus interconnected with said annulus for rotation in predetermined angular relationship thereto, a series of circumferentially-spaced axial rollers between the rotor and annulus subdividing the space therebetween linto aplurality of separate compartments, and a series of pockets in the periphery of the inner rotor each loosely confining one of said rollers for free movement independently of the other rollers toward and away from the axis of the inner rotor.

6. In a rotary pump, a housing, inner and outer rotors mounted therein, said rotors supported in eccentric relation whereby there is a crescentshaped gap between them, said housing having an intake port and a discharge port communicating with circumferentially spaced portions of said gap, the inner rotor having in its periphery a series of circumferentially spaced pockets each extending axially of the rotor, a roller mounted in each pocket for independent movement toward and away from the axis of the inner rotor, said rollers being maintained by centrifugal force in contact with the inner surface of said outer rotor, the bore of said outer rotor being provided with circumferentially spaced pockets for receiving said rollers whereby said rotors are interconnected by said rollers for rotation in predetermined angular relationship.

7. In a rotary pump, a pair of rotors supported in eccentric relation, one comprising a perforate annulus encircling the other, the inner rotor having around its periphery a series of spaced pockets and the annulus having around its interior a different number of pockets spaced to register consecutively with pockets of said inner rotor, each pair of registering fpockets containing an element disposed partly in one pocket of the Ipair and partly in the other, whereby the rotors are intermeshed for rotation together, said meshing elements carried by the pockets in said inner rotor and confined by said annulus for limited movement into and out of their respective pockets, and a pair of spaced-apart manifolds adjacent the exterior of the annulus each registering with the perforations in said annulus.

8. A pump as in claim 7 wherein the number of pockets in said outer rotor exceeds the number of pockets in said inner rotor by one.

9. A pump as in claim 7 wherein each of the perforations in said outer rotor extends radially outward from the bottom of one of the pockets in the outer rotor.

l0. A pump as claimed in claim 7 wherein said meshing elements are rollers paralleling the axes of the rotors.

l1. A pump as in claim 10 having a source of power connected to one of said rotors for turning both rotors in a particular direction, and a plurality of fluid passageways in the inner rotor each communicating at one end with the bottom of one of said pockets therein, the other end of the passageway for each pocket communicating with the peripheral space around the inner rotor at a point ahead of the roller in that pocket.

l2. A pump as in claim ll wherein each said passageway comprises a groove in the leading wall of one of said pockets.

13` A pump as claimed in claim '7 having a power driven shaft directly connected to only one of said rotors, the other rotor being driven by said one rotor through said meshing elements.

14. In a rotary pump, a pump cavity containing intermeshed ring and pinion gears, the meshing teeth of the pinion comprising independently rotatable rollers, intake and exhaust manifolds disposed adjacent the exterior of said ring, the respective manifolds being spaced apart circumferentially of the ring, and said ring having circumferentially-spaced ports each adapted 9 to Lregisteralternately with said intake and .exhaustinar'iif' ds as the ring rotates.

15. In a rotary pump, a pum-p cavity containing intermeshed ring andppinfion gears, said ring ha'vingon'efmore toothvthansaid pinion, the t`eeth of the .pinion ycomprising independently rota-table rollers, intake and. exhaust Vrrlan'rflds disposed 'adjacent the exterior of Vsaid ring the respective manifolds being spaced apart circumferentially of the ring and said ring having circumferentialfly-spaced ports l eachy adapted to vreg-gister alternately with said intake and exhaust manifolds as the ring rotates.

16. In a rotary pump, apu'rnp cavity containing-intermeshed ring and .pinion fig'ears, means for applying power to one of the'gears thereby to cause -both to rotate, intake and exhaust mani- @olds disposed adjacent the .exterior of said ring fgeai, 'the respective manifolds being spacedsapart r'dumferentially of the. ring, zsaid -ring gear lifaving ports each adapted to register alternately with said intake and exhaust manifolds as the ring rotates, said pinion having a circular hub with circumferentially spaced pockets in the .periphery thereof, the teeth of the pinion comprising independently rotatable rollers carried in said pockets, each pocket having in its leading wall a groove for admitting fluid past the assoelated roller into the bottom of the pocket.

17. In a rotary pump, a pump cavity containing intermeshed ring and pinion gears, the meshing teeth of the pinion comprising radially movable rollers, intake and exhaust manifolds disposed adjacent the exterior of said ring, the respective manifolds being spaced apart circumferentially of the ring and said ring having circumferentially-spaced ports each adapted to register alternately with said intake and exhaust manifolds as the ring rotates.

18. In a rotary pump, a pump cavity containing intermeshed ring and pinion gears, said ring having one more tooth than said pinion, the teeth of the pinion comprising radially movable vanes, intake and exhaust manifolds disposed adjacent the exterior of said ring, the respective manifolds being spaced apart circumferentially of the ring, and said ring having circumferentially-spaced ports each adapted to register alternately with said intake and exhaust manifolds as the ring rotates.

19. In a rotary pump, a pump cavity containing intermeshing ring and pinion gears, said pinion including a hub having in its periphery a series of circumferentially spaced grooves each extending axially of the hub, each tooth of said pinion comprising a cylindrical roller paralleling the axis of the hub and loosely confined in one of said grooves for free movement independently of the other rollers toward and away from said axis, fluid intake and exhaust manifolds dis- `posed adjacent the exterior of said ring gear, the respective manifolds being spaced apart circumvferentially of the ring, and said ring having circumferentially spaced ports each adapted to register alternately with said intake and exhaust manifolds as the ring rotates.

20. A pump as in claim 19 wherein the maximum distance between the periphery of said hub and the addendum circle of said ring gear is less than the radius of one of said rollers.

21. In a rotary pump, a pump cavity containing inter-meshing ring and pinion gears, the ring gear having one more tooth than the pinion, said pinion including a hub having in its periphery a series of circumferentially spaced grooves each 10 eieediegaxiellr Otite heb each. tooth @fraile ""mp'is'i"`g-acylindricalroller parallelng the-wwf 1110er si@ 1S and exhaust `r'rnai'flds Y fe exterior of `said ring gear, tHe li'S'D' t'Ie :manifolds being spaced apart 4Fc V nnf of the r g' vand lsaid ring hay'ilgcir'- ld ports each 'adapted fto atelyI withjsaid -i'n'take and exhaust "maar ,Qlfds .Y r asin eiaiirrzi whereih-sadfours A"aire of "e'iial radius and the depth o'f he teeth of said ring gear is less than salidradifs.

243., Ina rotary pump, a pair of eccentric rotors. one 'comprising 'a prwforate annulus encircling the other with its bore substantially engaging the periphery of the inner rotor at one point whereby there is a crescent shaped gap between the two rotors, said gap being of maximum size at a point diametrically opposite said point of engagement, the inner rotor having in its periphery a series of circumferentially spaced grooves each extending axially of the rotor, a plurality of identical cylindrical rollers paralleling the axis of the inner rotor and each loosely confined in one of said grooves for independent movement toward and away from said axis, said rollers being free of one another and each tending to ny out of its associated groove due to centrifugal force as it travels with the rotor, said gap between the two rotors being, at said point of maximum size, less than the radius of each roller whereby the rollers always are retained in their respective grooves while bearing against the interior of said annular rotor due to centrifugal force, said annulus having in its bore a series Yof circumferentially spaced grooves each extending axially of the annulus for receiving said rollers, the depth of said last grooves being less than the radius of each roller, the number of said last grooves being greater than the number of grooves in said inner rotor, each of said rollers adapted as it passes said point of engagement between the two rotors to enter a groove in said annulus whereby the rotors are intermeshed for rotation together and the grooves in the annulus. register consecutively with the grooves in the inner rotor as they pass said point of engagement, and a pair of spaced apart manifolds adjacent the exterior of said annulus each registering with the perforations in said annulus.

24.. A rotary pump as in claim 23 wherein the diameter of each roller is substantially equal to the aggregate depth of a pair of said grooves, one groove of the pair being in the inner rotor and the other in said annulus.

25. In a rotary pump, a housing having a circular bore, a perforate annular rotor journaled in said bore with the exterior of the rotor and the wall of said bore forming complementary bearing surfaces, an inner rotor within said annular rotor mounted in eccentric relation thereto whereby there is a crescent-shaped gap between the two rotors, said housing having an intake port and a discharge port communicating via the perforations in said annular rotor with circumferentially spaced portions of said gap, said ports comprising a pair of circumferentially spaced channels in the wall of said bore each registering with the perforations in said annular rotor, the inner rotor having in its periphery a series of circumferentially spaced pockets each extending axially of the rotor, a roller mounted in each pocket for free movement independently of the other rollers toward and away from the axis of the inner rotor, Said rollers being maintained by centrifugal force in Contact with the inner surface of the annular rotor thereby to subdivide said gap into a plurality of separate compartments, the width of each pocket being substantially eq-ual to the diameter of the roller in that pocket whereby bodily movement of the rollers relative to the inner rotor is conned to inward and outward movement in said pockets and a substantially fluid-tight seal is maintained at all times between each roller and the wall of its respective pocket.

CHARLES L. ENGLISH.

Number Name Date Ripberger July 27, 1909 Hill Mar. 11, 1924 Nicholsv Jan. 6, 1931 Hill Aug. 14, 1934 Kempton Sept. 4, 1934 Tucker Aug. 18, 1942 Looke Jan. 25, 1949 FOREIGN EATENTS Country Date Great Britain of 1892 Switzerland Nov. 1, 1922 Great Britain of 1928 Great Britain June 29, 1933 Great Britain Jan. 18, 1934 France Aug. 4, 1939 

